Love it or hate it, daylight saving time should be nothing to lose sleep over

Daylight saving time returns Sunday morning, reviving concerns about the tradition’s health impacts, along with debate about whether the benefits of turning the clock ahead an hour every March outweigh the downsides.

While many complaints about daylight saving time center on losing an hour of sleep and getting up while it’s still dark, Bethany Dillen, Ph.D., a professor in Metropolitan State University of Denver’s Department of Psychological Sciences, said turning the clocks ahead can disrupt the body’s natural cycles.

“We use the daylight as the regulator of our circadian rhythm,” she said. “It helps release the melatonin that makes us sleepy, and it can make it harder to wake up in the morning when it’s still dark out.”

Daylight saving time also can create a disconnect between the natural circadian rhythm and the light cycle, she said.

Scientists know that exposure to natural light activates a “master clock” in the brain. That master clock, in turn, synchronizes other “clocks” in organs throughout the body, regulating metabolism and the release of hormones.

“There’s a large body of research on how sleep deprivation and sleep disturbances affect our ability to perform activities and can impair our cognitive functioning,” Dillen said.

Children may experience mood shifts, irritability and difficulty concentrating due to daylight saving time, said Dillen, who specializes in child developmental psychology. “But you wouldn’t see that being a significant problem unless it was long term,” she said.

“At least for children, the best way to mitigate the problem is, starting the weekend before, bump the kids’ bedtime by 10 minutes and their wake time by 10 minutes each day leading up to the start of daylight saving — they get that gradual shift,” she said. “It can mitigate a lot of the problems.

“But…I’m a parent of two young kids. It’s really hard to predict what time my kids are going to go to bed down to the 10-minute mark.”

Adults might experience similar mood problems, especially if they already are having sleep difficulties, she said. “The irritability, the mood disturbances — that’s all going to be related to hormones and to neurotransmitters and speaks to the importance of sleep in general,” Dillen said.

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Daylight saving time was first introduced temporarily in the United States during World War I to conserve energy. It returned during World War II and was standardized in 1966.

The debate over daylight saving time is practically as old as the practice itself.

Arizona and Hawaii don’t observe daylight saving time at all. These days, many others agree that turning the clocks ahead in the spring and back in the fall makes little sense.

Others, including the Colorado legislature, argue for daylight saving time year-round.  In 2022, the Colorado General Assembly passed legislation to adopt daylight saving time year-round, but it was contingent on federal authorization and similar changes by at least four other states in the Mountain time zone.

Some of the strongest advocates for daylight saving time have been school districts, Dillen said, “because it allows students to be involved in extracurricular activities such as athletics after school, and they have data that shows the benefits of those extracurricular activities on kids,” Dillen said. “It’s real, undeniable data, and they’re not wrong. But the question is always: How many kids are you impacting with those programs versus how many kids are you impacting with daylight saving time?”

On the other hand, the American Academy of Sleep Medicine has advocated for year-round standard time on the grounds that “it best aligns with human circadian biology.”

“Evidence supports the distinct benefits of standard time for health and safety, while also underscoring the potential harms that result from seasonal time changes to and from daylight saving time,” the academy wrote.

In its statement, published in January 2024 in the Journal of Sleep Medicine, the academy also pointed to a number of adverse biological effects from the spring time change, including “higher heart rate and blood pressure, immune system alterations, and a variety of cellular derangements…”

Dillen acknowledges that individual factors impact how people feel about and respond to springing forward and falling back, such as “how much sleep you’re already getting and what time your shift is at work.”

Still, Dillen is partial to the existing practice of alternating between standard time and daylight saving time. “Even though the switch is disruptive for that week or two each year, I still think that you can mitigate that if you plan right to outweigh the costs.”